[ash-md] Adds support for Z-order iteration in views::View

ui/views/view.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_VIEWS_VIEW_H_
 #define UI_VIEWS_VIEW_H_
 
 #include <stddef.h>
 
 #include <algorithm>
@@ skipping 174 matching lines @@
   void ReorderChildView(View* view, int index);
 
   // Removes |view| from this view. The view's parent will change to NULL.
   void RemoveChildView(View* view);
 
   // Removes all the children from this view. If |delete_children| is true,
   // the views are deleted, unless marked as not parent owned.
   void RemoveAllChildViews(bool delete_children);
 
   int child_count() const { return static_cast<int>(children_.size()); }
+  // See also |GetChildrenInZOrder()| below that returns |children_|
+  // in reverse z-order.
   bool has_children() const { return !children_.empty(); }
 
   // Returns the child view at |index|.
   const View* child_at(int index) const {
     DCHECK_GE(index, 0);
     DCHECK_LT(index, child_count());
     return children_[index];
   }
   View* child_at(int index) {
     return const_cast<View*>(const_cast<const View*>(this)->child_at(index));
@@ skipping 96 matching lines @@
   virtual bool IsDrawn() const;
 
   // Set whether this view is enabled. A disabled view does not receive keyboard
   // or mouse inputs. If |enabled| differs from the current value, SchedulePaint
   // is invoked. Also, clears focus if the focused view is disabled.
   void SetEnabled(bool enabled);
 
   // Returns whether the view is enabled.
   bool enabled() const { return enabled_; }
 
+  // Returns the child views ordered in reverse z-order. That is, views later in
+  // the returned vector have a higher z-order (are painted later) than those
+  // early in the vector. The returned vector has exactly the same number of
+  // Views as |children_|. The default implementation returns |children_|,
+  // subclass if the paint order should differ from that of |children_|.
+  // This order is taken into account by painting and targeting implementations.
+  virtual View::Views GetChildrenInZOrder();
+
   // Transformations -----------------------------------------------------------
 
   // Methods for setting transformations for a view (e.g. rotation, scaling).
 
   gfx::Transform GetTransform() const;
 
   // Clipping is done relative to the view's local bounds.
   void set_clip_path(const gfx::Path& path) { clip_path_ = path; }
 
   // Sets the transform to the supplied transform.
@@ skipping 1270 matching lines @@
   // Observers -------------------------------------------------------------
 
   base::ObserverList<ViewObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(View);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_VIEW_H_